NEW YORK: Andy Roddick celebrated his 30th birthday on Thursday by announcing his retirement as Roger Federer, the great Grand Slam tormentor of the American, eased into the third round at the US Open.

Roddick, a former world number one, who won his only major title in New York in 2003, admitted his level was struggling to match the big three of Federer, Rafael Nadal and Novak Djokovic and he will quit once the US Open is over.

“I have decided that this is going to be my last tournament,” said Roddick, who is guaranteed an emotional reception on Arthur Ashe Stadium on Friday night when he plays Australia's Bernard Tomic for a place in the last 32.

“I feel it is the right time to do it. These other guys have gotten really, really good and I'm not interested in just existing on tour. I don't want to disrespect the game by coasting home.”

Roddick's annoucement came a day after Kim Clijsters, a four-time Grand Slam champion, suffered a second round defeat which sent her into retirement.

Roddick, whose ranking is now down at 22 in the world, lost to Federer in the Wimbledon finals of 2004, 2005 and 2009.

That last All England Club defeat, an epic match which ended 16-14 in the fifth set, was Roddick's last memorable campaign and he has not got beyond the quarter-finals of a Grand Slam since.

Top seed and five-time champion Federer reached the last 32 with an easy 6-2, 6-3, 6-2 win over Germany's Bjorn Phau and next faces Spain's Fernando Verdasco, whom he has beaten four times in four matches.

Federer, bidding to become the first man to win six New York titles in the Open era, clinched the 90-minute match with his 15th ace after also firing 44 winners past the 32-year-old Phau, the world number 83.

“Andy's a great man,” Federer said. “I had some great battles with him for a long, long time and all the Wimbledon finals come to mind. We had some epic battles over the years.

“But he got the last laugh – he beat me in Miami this year.”

Two-time women's champion Venus Williams was knocked out, losing 6-2, 5-7, 7-5 to German sixth seed, and 2011 semi-finalist, Angelique Kerber, who also knocked the American out of the Olympics.

Kerber has now won a tour-leading 55 matches in 2012.

“It was unbelievable, it was such a tough match and very close. Venus is such a great player and has won so many Grand Slam titles,” said Kerber, who benefitted from Williams committing 60 unforced errors.

Defeat for seven-time Grand Slam title winner Williams meant 2012 was the first year in her career that she failed to get beyond the second round of any of the four majors.

“She's playing great but I didn't help myself a lot,” said Williams. “I tried to be aggressive but it's hard to be aggressive when every shot you hit goes out.”

Sister Serena, the three-time champion, won her 60th match at the US Open, advancing to the third round with a 6-2, 6-4 victory over Spain's Maria Jose Martinez Sanchez.

Williams, the Wimbledon and Olympic champion, will next face Russia's Ekaterina Makarova, who beat her at the Australian Open this year.

Second seed Agnieszka Radwanska, who was Wimbledon runner-up to Serena, almost suffered a fourth successive second-round exit before fighting back from a set and 3-1 down to beat Spain's Carla Suarez-Navarro 4-6, 6-3, 6-0.

Radwanska goes on to face Serb 30th seed Jelena Jankovic, the 2008 runner-up, who made the third round with a 6-4, 6-2 win over Spain's Lara Arruabarrena-Vecino.

French fifth seed Jo-Wilfried Tsonga, who reached the quarter-finals in 2011, was the highest men's seed to fall when he slumped to a shock 6-4, 1-6, 6-1, 6-3 defeat to unheralded Slovak Martin Klizan.

The flamboyant, shot-making Frenchman had come into the final Grand Slam event of the season in a fog of injury and form worries, summed up by having to skip the Cincinnati event after cutting his knee on a fire hydrant.

“Today I was not in good shape. I didn't play good tennis,” said the 27-year-old Tsonga. Left-hander Klizan, the world 52, progressed to the third round of a Grand Slam for the first time and will tackle 32nd seed Jeremy Chardy of France.

Men's sixth seed Tomas Berdych eased past Estonia's Jurgen Zopp 6-1, 6-4, 6-2 and faces America's Sam Querrey next.

Spanish 11th seed Nicolas Almagro fought back to beat Philipp Petzschner 6-3, 5-7, 5-7, 6-4, 6-4 with the German's challenge undone by 62 unforced errors.

American 23rd seed Mardy Fish, a quarter-finalist in 2008, beat Russia's Nikolay Davydenko, a semi-finalist in 2006 and 2007, in a gruelling five-setter.

His 4-6, 6-7 (4/7), 6-2, 6-1, 6-2 win was the 10th comeback victory from two sets-to-love down in the men's tournament this year.